Having integrated our instruments onto the DC8-8, and tested them in the hangar the only thing left to do before the mission proper was see how everything performed in flight.
First, the crew conducted a shakedown flight without scientists just to check that everything was integrated safely, and then we went up for our first test flight. This was my first time flying in a research plane. Some more experienced scientists delighted in telling me horror-stories of maneuvers and low-flying turbulence making people ill before we took off. I was nervous, mainly about how my instruments would perform, as there are controls for things like pressure and flow that I can’t test on the ground, and also because I didn’t want to embarrass myself by getting ill on the test flight.
We flew from the base out over the Pacific, then back inland over the LA-Basin and back to base. The ATom mission flights will be constantly profiling between about 0.2 and 12km altitude, so we did a lot of ascending and descending to check that the instruments can cope with it and to look at the fuel performance of the plane with this payload. To really test every instrument, the pilots did some really fast ascents and descents (for example, flow into the inlets is affected by the incline). I had to be up out of my seat testing some things on the instrument during part of this: the crew really weren’t joking when they said to hang on.
Our instruments behaved well, needing just one or two quick software fixes that I was able to implement as we flew, and I started to relax and enjoy the flight. We can stream video from cameras in the cockpit and one looking directly down below the plane, which is great. We also have a window by my seat, so I can look out.
Once over the Pacific and out of the LA-area high air traffic we dropped seriously low, had there been a whale breaching below I would have easily seen it. We also did some very low flying over the central valley, which produced interesting data and interesting views (although also a reasonable amount of turbulence).
During the flight we had to do some maneuvers. These are used to calibrate instruments measuring wind-speed. The crew advised us to sit down for these, and I’m glad I did, as some of them had my body weight almost out of the seat and pulling on the seatbelt. If you throw a small object in the air during one of the maneuvers you can watch it appear to hover as it falls under gravity but the you and the plane also move down away from it. It felt a bit like being in a roller coaster, and by the end of all the maneuvers I was glad to return to more normal flight. It can make you a little queasy, but just eating something or walking about the cabin afterwards really helps.
The aircraft is noisy in flight, partly because there is less insulation on it than on a normal passenger plane, and partly because of all the pumps and fans etc. on our instruments. We therefore all wear headsets, which cancel background noise and enable us to communicate with other scientists and the crew. We get some bleed-over from the channel the pilots are on, which is quite fun.
I was quite surprised when we arrived back already, four hours of flight goes by so quickly when you’re operating instruments and concentrating on the science behind what you’re seeing compared to a passenger flight. It was a good feeling to have a successful flight under the belt, to see that the instruments worked as expected and that my body coped fine with the flying conditions. We have one more test-flight just before we take off for the mission-proper. I’m looking forward to it!